In recent years, miniaturization and weight reduction have been strongly demanded for batteries used as power sources for electronic devices, automobiles, and the like. With respect to a package for batteries, laminate films have been increasingly used, instead of the conventional metallic cans. As a laminate film, generally known are those using aluminum as a metal thin film, and nylon (registered trademark) or polyethylene terephthalate for the outer surface of the battery, and polyethylene or polypropylene for the inner surface as a fusion bondable resin film. A film package battery is obtained by enclosing a battery element together with an electrolyte in an outer package (also referred to as “film package”) made of such a laminate film.
In such a film package, there is a problem that when a large shock is applied to the battery, for example, during use or transportation of the battery, the internal battery element is displaced, and as a result, electrode tabs and the structure therearound may be damaged. As a technique for fixing the battery element to the film package, for example, Document 1 discloses that a fixing tape is attached to a stacked battery element and that fixing tape is thermally fused and bonded to the outer package.